dovecot: replace solr fts with flatcurve (xapian) (#5680)

* fts-flatcurve: inital implementation

* fts: removed solr from compose.yml

* flatcurve: added heap and proc logic to dovecot

* added logic for update.sh & generate for Flatcurve

* delete old iteration of fts-flatcurve.conf

* updated default fts.conf

* updated .gitignore to exclude fts.conf for further git updates

* Remove autogeneration of fts.conf (disable override)

* cleanup all left solr stuff

* renamed SKIP_FLATCURVE to SKIP_FTS

* cleanup leftovers solr in lang files

* moved lazy_expunge plugin only to mail_plugins

* added fts timeout value

* compose: remove dev image of dovecot

* updated japanese translation

.github/workflows/image_builds.yml

@@ -23,7 +23,6 @@ jobs:
           - "postfix-mailcow"
           - "rspamd-mailcow"
           - "sogo-mailcow"
-          - "solr-mailcow"
           - "unbound-mailcow"
           - "watchdog-mailcow"
     runs-on: ubuntu-latest